1. Field of the Invention
The present invention relates to a polarized lens reduced in weight and thickness for making glasses convenient to wear.
2. Prior Art
Sunlight is a mixed wave of a longitudinal wave and a transversal wave, and a polarized lens having an optical anisotropic aspect is configured to select one of oscillating waves from the longitudinal wave and the transversal wave and allow the selected wave to pass through and block the other wave from passing therethrough when the sunlight passes through the polarized lens. Therefore, the polarized lens prevents glaring of water surfaces, road surfaces, or roof tiles due to reflected sunlight, protects wearer's eyes from blinding light, and is an optimum lens for the strong sun in summer. If only shielding the sunlight is wanted, sunglasses will do. However, the sunglasses do not have a function to block one of the oscillating waves of the sunlight, and hence cannot prevent the glaring of the reflected light completely.
The polarized lens has a structure in which a polarized film is laminated on a transparent glass layer. FIG. 3 illustrates a cross section of a general polarized lens of the prior art, in which a front side glass lens “a”, a back side glass lens “b”, and a polarized film “c” are laminated. When light enters the front side glass lens “a”, one of the oscillating waves, that is, one of the transversal wave and the longitudinal wave, is blocked by the polarized film “c” from passing therethrough, and one of the oscillating waves is allowed to pass through the back side glass lens “b”. Here, the thickness of the front side glass lens “a” is approximately 1.0 mm, and the thickness of the back side glass lens “b” is approximately 1.0 mm, so that a generally thick lens is achieved.
Although the polarized film “c” is very thin and hence is lightweight, the front side glass lens “a” and the back side glass lens “b” are thick and heavy. Therefore, the weight of the polarized lens having a laminated structure as illustrated in FIG. 3 is increased, and the front portion of the glasses becomes heavy. In particular, such a structure does not conform to a requirement of glasses of recent years in which lightweight glasses have become mainstream. Even though the weight of the frame structure is reduced,such a reduction of the weight makes no sense if the lenses to be fitted into rims of the front portion of the frame are heavy.
A polarized lens having a polarized film sandwiched between plastic lenses (resin lenses) is also known. If the plastic lens (resin lens) is employed, the weight is reduced in comparison with the glass lens. However, a stiffness of the polarized lens is lowered. Therefore, when fitting the polarized lens of this type to the rim, internal distortion may occur due to differences in rim shape and dimensions, whereby polarizing performance may deteriorate.
“Polarized lens and method of making polarized lens” disclosed in JP-T-2011-501235 (WO2009/054835) describes a polarized lens including a polarized polyvinyl alcohol (PVB) film, a first epoxy layer on one surface of the PVB film, and a second epoxy layer on the other surface of the PVB film, wherein the combined PVB film and the epoxy layers are practically prevented from breakage, cracking, or optical deformation.
“Spectacle lens equipped with polarizing function and electromagnetic wave preventing function” disclosed in JP-A-2005-121697 provides a polarized lens having a polarized base body and triacetate films stuck to both surfaces thereof, wherein a metal is attached to a surface of a woven fabric or the like such as polyester, a conductive mesh applied with copper plating and black plating thereon is placed on the polarized base body and then is laminated with triacetate films so as to block an electromagnetic wave.
In this manner, although technologies relating to the polarized lens are known, there is no lightweight polarized lens with a thin profile. Since the polarized lens has a sandwich structure in which a polarized film is sandwiched from both sides, the weight is increased by necessity. Although the glaring water surfaces, road surfaces, or roof tiles due to reflected sunlight are prevented and wearer's eyes are protected from blinding light of the strong sun in summer, problems of the weight of the glasses being increased, or the thickness of the polarized lens increased still exist.